Video and image sequences with alpha channels can be straight or premultiplied. If you’re working with video or image sequences containing alpha channels, it’s important to specify how Photoshop Extended interprets the alpha channel to get the results you expect. When premultiplied video or images are in a document with certain background colors, you may get undesirable ghosting or halos. You can specify a matte color so the semi-transparent pixels blend (multiply) with the background without producing halos.

Ignore

Ignores the alpha channel in the video.

Straight - Unmatted

Interprets the alpha channel as straight alpha. If the application you used to create the video doesn’t premultiply the alpha channel, select this option.

Premultiplied - Matte

Interprets the alpha channel as premultiplied with black, white, or a color. If necessary, click the color swatch in the Interpret Footage dialog box to open the Adobe Color Picker to specify the matte color.